What is HSRP and VRRP?
Answer
HSRP (Hot Standby Router Protocol) and VRRP (Virtual Router Redundancy Protocol) are First-Hop Redundancy Protocols (FHRPs) that provide a virtual default gateway IP address shared between multiple physical routers. If the active router fails, the standby router takes over within seconds, maintaining connectivity. HSRP is Cisco-proprietary. An active router and standby router share a virtual IP and virtual MAC address. Hosts use the virtual IP as their default gateway. If the active router fails, the standby becomes active after a hold timer expires. VRRP (RFC 5798) is the open standard equivalent — one master and multiple backup routers share a virtual IP. GLBP (Gateway Load Balancing Protocol) is Cisco's improvement that load-balances across multiple routers rather than having one idle standby. All three provide sub-second failover with proper tuning, making the gateway transparent to end users.